Photovoltaic and Barrier Properties of Au/n-Ge Schottky Junction Modified by Methylene Blue Organic Dye Interlayer

Photovoltaic and barrier characteristics of methylene blue (MB) organic dye modified Au/n-Ge Schottky junction were investigated. The physical properties of MB layer were evaluated using optical, structural and morphological studies. The MB layer shows strong optical absorption at 308 nm and 601 nm implying an optical bandgap of 3.05 eV and 1.45 eV respectively. The morphology of the MB layer on the Ge substrate shows a very smooth surface with a uniform distribution of grains. The structural property of the MB layer analysed using FTIR measurement indicates various distinguished bonds signify the structure of organic layer. Comprehensive analysis of interfacial parameters, including the ideality factor (n), barrier height (Φ_b) and series resistance (R_S) are extracted for both Au/n-Ge contact and MB/n-Ge heterojunction using current-voltage (I-V) and capacitance-voltage (C-V) approaches. Notably, the heterojunction exhibits a significantly enhanced rectification ratio and very low R_S compared to the Au/Ge contact, making MB a promising candidate for Schottky device based photovoltaic cells. The barrier parameters were checked for consistency with other approaches such as Cheung and Norde methods. Additionally, the study also explained the impact of the MB interlayer on the density of interface traps/states (N_ss) of Au/n-Ge junction. The photovoltaic properties of the MB/n-Ge heterojunction were analysed under different illumination powers. The photovoltaic cell parameters and the barrier parameters were examined under illumination for different optical power. The fill factor of the heterojunction shows a larger magnitude at 60 mW/cm².